The present invention relates generally to improved lighting fixtures having both a transmitted and reflected light component employing a material, such as, a polymeric material which has an appearance, in varying degrees, of white.
As used in the present description and claims, the term lighting fixture includes luminaries and indoor and outdoor lighting fixtures. Typically a lighting fixture includes a light source, a light reflecting member, such as, a reflector, and/or a light transmitting member, such as, a refractor, a lens, or an enclosure and/or a partially reflective partially transmittive optical component.
At present there are few choices in creating efficient lighting fixtures which have a partially reflective partially transmittive optical component.
At present, many fixtures utilize acrylic, polycarbonate or glass prismatic reflectors which provide the benefits of uniform distribution, vertical illumination, glare control and a diffuse transmission component which serves to reduce apparent brightness of the fixture, by lighting the ceiling above the fixture. In comparison, aluminum or painted steel reflectors are opaque and thus cannot provide a uniform diffuse transmission or vertical illumination component, and apparent brightness is much higher, causing discomfort glare. Perforated aluminum or steel reflectors have not enjoyed success as an alternative as the holes collect excessive dirt and the optical system cannot be readily enclosed. A limitation of the prismatic reflectors mentioned above is the relatively high percentage of diffuse transmission. Even the best acrylic prismatic reflectors generally exhibit diffuse transmission of 20% of total fixture output. When used with larger sources, such as multiple compact fluorescent lamps, the percentage is closer to 30%. Translucent pigmented white reflectors have been produced, but they too have had diffuse transmission components of approximately 25-30%.
U.S. Pat. No. 5,596,450 issued Jan. 21, 1997 to Hannon et al. and assigned to W. L. Gore and Associates, Inc. discloses an expanded polytetrafluoroethylene (PTFE) material. The expanded PTFE in a film can be highly reflective, in the range of 98.5%, and still have a small amount of transmission, about 1.5%. However, this material and process are expensive and primarily suited to two-dimensional applications.
A need exists for an improved lighting fixture having both a transmitted and reflected light component. It is desirable to provide a lighting fixture component with reduced diffuse transmission, while not completely eliminating it. The benefits of such a product include better coefficients of utilization, improved horizontal footcandles, and reduced glare. In outdoor applications it also provides improved shielding angles and reduced contribution to sky-glow versus typical vertical refractors.
A principal object of the present invention is to provide an improved lighting fixture having both a transmitted and reflected light component employing a polymeric material which has an appearance, in varying degrees, of white. Other important objects of the present invention are to provide such improved lighting fixture having both a transmitted and reflected component employing a polymeric material which has an appearance, in varying degrees, of white substantially without negative effect and that overcome many of the disadvantages of prior art arrangements.
In brief, a lighting fixture is provided. The lighting fixture has both a transmitted and reflected light component employing a polymeric material which has an appearance, in varying degrees, of white. The material has internal elements which can be varied to be either highly reflective or permit efficient diffuse transmission of incident light rays. The ratio of reflected to transmitted light and the degree of diffusion are tailored to the application, light source and desired appearance. The material is adapted for providing a selected diffuse transmission component of total fixture output.
In accordance with features of the invention, the material provides a set diffuse transmission component of greater than 1% and less than 25% where the material is formed by pigmenting a transparent material with a white pigment. The material provides a set diffuse transmission component of greater than 1% and less than 99% where the material is formed by a foamed polymeric material, by an expanded bead material, by blending transparent materials having different refractive indices, or by adding a filler to a polymeric material.